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Metasurfaces have gained a considerable amount of interest in the past decade for their capabilities to manipulate electromagnetic (EM) waves in different manners. They have offered multiple functionalities in terms of wave control depending on the given application. In terms of wave control, particularly EM beam splitting, it can be challenging compared to the given literature review, to achieve a wide number of beam-splitting reflections and coverage for multiple incident angles simultaneously. In this paper, we focus on the design of a metasurface based on the methodology of high periodicity supercell design (5.76 λ) and impedance modulation to achieve a various number of beam-splitting angles, while maintaining the same coverage at multiple incident angles for millimeter-wave (mm-Wave) frequencies. Following the generalized phase law of reflection alongside proper optimization of the surface impedance, the proposed reflective anomalous beam splitter (RABS) metasurface is designed to be polarization independent, and high reflection efficiency is achieved with a wave beam split into 11 different directions while operating for multiple incident angles simultaneously, making it a promising candidate to overcome challenges for various mm-Wave communication applications, especially in expanding 5G coverage in non-line of sight regions at a 28 GHz frequency band. The performance of the RABS metasurface is evaluated using both full-wave simulations and experimental measurements, which demonstrate its effectiveness in achieving 11 efficient reflective anomalous beams with a reflection efficiency of up to 96.65% and 97.36% in TE and TM modes at 28 GHz. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) RF (radio frequency) energy harvesting in dynamic ambient environments is a challenge for conventional energy harvesting systems such as rectennas. The main challenges are the low efficiency of the collector and low ambient power levels, which makes it hard to consider in industrial applications. Several research works have focused on the design of high-efficiency antennas to achieve an efficient and maximum possible level of RF EM energy harvesting. Their main objective is to improve the EM energy harvesting system by overcoming the low efficiency of the collector, which is the main part of the rectenna system. In this work, we propose and investigate a methodology in terms of EM energy harvesting based on the concentration and focusing of EM energy in a small zone where it can be easily collected and transferred indirectly to the rectenna system. It consists of a focusing device and a methodology to associate the latter with existing RF energy harvesting systems. We demonstrate a focusing metasurface design implemented alongside an off-the-shelf rectenna device at 900 MHz, where an enhanced energy harvested power level up to a linear gain of 8 is achieved compared to the case when only the rectenna is used. Numerical results as well as measurements results in an anechoic chamber are shown. Experimental power received levels are given both in the focusing plane and in time for the validation of the concept. [ABSTRACT FROM AUTHOR]

In this paper, a cascaded retrodirective metasurface is designed and demonstrated to operate simultaneously at a wide range of incident angles from − 30 ° to − 10 ° and 10 ° to 30 °. It is based on the design of several retrodirective super-cells following the generalized Snell's law of reflection, where each super-cell is designed to redirect an incoming wave back in the same direction with high efficiency. This metasurface is a very good candidate as a retroreflector for radar cross-section (RCS) enhancement of targets with poor backscattering. Retrodirective topologies have been a subject of interest, and several engineered topologies exist, such as the corner dihedral. Despite their good performances at a range of incident angles, their 3-dimensional bulky structure makes them hard to implement for different applications and they do not address extreme incident angles. The metasurface proposed can be a complementary solution to existing topologies for addressing extreme oblique incident angles while being more compact due to its two-dimensional subwavelength structure design. The monostatic radar cross-section (RCS) performance of the designed metasurface of dimensions 8.163 × 56.23 cm 2 has been compared to that of a conventional corner dihedral of dimensions 8 × 15.5 × 7.75 cm 3 , and a gain of up to 50 dB of monostatic radar cross section (RCS) in the ranges − 30 ° to − 20 ° and 20 ° to 30 ° was obtained. Comparable performances are observed in the ranges − 20 ° to − 10 ° and 10 ° to 20 ° between the designed metasurface and the corner dihedral. Experimental results are shown to be in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

We present a numerical study of resonant negative refractive index (NRI) metamaterials in which their effective parameters are calculated. For a periodic media consisting of split-ring resonators and metallic wires the effective refractive index is compared by means of two different methods. The first one is an inversion procedure in which the effective refractive index is calculated from the reflection and transmission coefficients of a finite structure and the second one consists its calculation from the phase velocity issued from the dispersion diagram. A significant difference between the two cases is highlighted in the frequency interval of interest (NRI regime) and for the finite media, counterintuitive observations are made. These anomalous features are observed in a frequency range in which there is a non-negligible contribution of the higher-order modes to propagation inside the periodic metamaterial. Hence in this particular frequency interval, the media cannot be described by an effective refractive index in a Fresnel sense. In other frequency regions, both methods converge and it will be shown that the metamaterial exhibits a negative refractive index. [ABSTRACT FROM AUTHOR]

The in-phase radiation from a conformal metamaterial surface is numerically and experimentally reported. The LC-resonant metasurface is composed of a simultaneously capacitive and an inductive grid constituted by copper strips printed on both sides of a dielectric board. The metasurface is designed to fit a curved surface by modifying its local phase. The latter phase-compensated metasurface is used as a reflector in a conformal Fabry-Pérot resonant cavity designed to operate at microwave frequencies. Far-field measurements performed on a fabricated prototype allow showing the good performances of such a phase-compensated metasurface in restoring in-phase emissions from the conformal surface and producing a directive emission in the desired direction. [ABSTRACT FROM AUTHOR]